The invention relates to a device and a method for inspecting a volume and/or the composition of a sample, in which an interface is formed in a pipette between the sample and a first fluid which is adjacent to the sample, said interface being optically perceptible outside the pipette as an interface line between the sample and the first fluid that extends essentially horizontally. The invention further relates to the use of a camera with a marking in an image field of the camera to carry out such a method.
In DE 10 2008 022 835 B3, a device is described as an analyser for analysing biological or chemical samples using a reagent liquid added via a pipette. A work plate is arranged so that it can be horizontally pivoted on a base plate to retain the samples in a sample holder, for example, a microtitre plate, which features several cells to retain the samples. The cells are also called slots, cavities or wells, occasionally also droplets. Arranged above the work plate is a robot manipulator, which has a horizontal support arm with a slide, said slide having a needle system attached that moves in a vertical direction. The needle system comprises several hollow needles as pipettes, which come to a stop at the same time over a single well, whereby one of the hollow needles pours the reagent liquid into the well. After a reaction or incubation time the solution, which is made of the sample in the well and the added reagent liquid, is suctioned off by a second hollow needle, supplied with a washing solution by a third hollow needle, and then suctioned off again by the second hollow needle. Using the three hollow needles, a single well is therefore supplied with reagent liquid and washing solution. The analyser itself does not contain any elements for evaluating the sample or solution in the well, said sample or solution is evaluated at a later stage by an expert. The wells with the samples or solutions feature barcodes to identify them, with the analyser featuring a device to read these barcodes in its rear section. When reacting with the reagent liquid the samples undergo a colour change and/or a fluorescence, which can be analysed and/or evaluated using a photometer for measuring colour.
As a result of the great number of solutions that are to be produced from a sample and a reagent liquid, which need to be produced as part of complete test series, it is necessary to produce these solutions under stable process conditions at high process speed and by using as low quantities as possible for the sample and the reagent liquid. In addition, the wells should be loaded in as simple a manner as possible for cost reasons. The analyser described above is disadvantageous inasmuch as the needle system with three needles as pipettes only adds a reagent liquid to a well in the amount to be pipetted and the amount that is to be pipetted is set via a drive associated with the first needle, which only guarantees the required process accuracy in terms of the quantity being set to a limited extent.